Implanted devices, such as heart pacers and cochlear implants, have been widely deployed to assist with the management of various indications. The present invention is particularly concerned with devices which are electrically powered.
Engineers and technicians have, with improvements in technology and knowledge, been making the devices smaller and therefore more readily implantable. Improvements to functions and the increased complexity of devices and functions are an important part of the progressive development of implantable devices. However, as implantable devices become increasingly complex, the potential for electrical failures increases.
Such failures can result in DC current leakage, with the excess DC current passing through tissue of the implantee in ways which are not related to therapy. Such DC currents flows could result in electrolysis, or otherwise cause injury to the user. DC currents can also cause irreversible redox reactions at the electrodes of the implanted device.
By way of example, current cochlear implants are capable of detecting fault conditions in only a very limited way, usually by regularly checking for particular faults. The faults being checked for are programmed into the implant based on the failure modes determined by the design team. For example, electrodes may short to ground. As devices become more complex, the number of failure modes that can lead to DC current leakage increases dramatically. As such, the present methods of checking for faults will take an increasing amount of time and power, and be increasingly complex to design and operate. Further, it becomes increasingly difficult to determine all possible failure modes, and to try to detect each specific failure mode.
It is accordingly an object of the present invention to provide a simplified method and apparatus for detecting current leakage in implantable devices.